Regulator system



Aug. 4, 1942. HQUCK I 2,292,123

REGULATOR SYSTEM Filed April 5, 1941 WITNESSES: INVENTOR fimes/Pflaucar.

ATTORNEY Patented Aug. 4, 1942 REGULATOR SYSTEM James P. Houck, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a. corporation of Pennsylvania Application April 5, 1941, Serial No. 387,046

8 Claims.

My invention relates to a furnace regulator system and more particularly to means for adjusting the setting of the regulator upon changes in the operating conditions of the circuit supplying energy to the furnace.

In the operation of electric arc furnaces of the movable electrode type, it is customary to provide a motor-operated mechanism for each electrode for raising and lowering the electrode as controlled by a regulator that is automatically responsive both to the value of current flowing in the electrode circuit and also to the voltage conditions in the electrode circuit. Such operation is desirable in order to obtain constant electrode arcs and even heating effects by the various electrodes connected to the several conductors of an alternating-current polyphase circuit supplying the furnace.

In the operation of melting furnaces, it is necessary to operate the furnace at a relatively high voltage during the early stages and, as the melting down process proceeds and the resistance of the material in the furnace decreases, to lower the applied voltage. This may be done by changing the tap connections of the transformer supsupply voltage to the furnace, and a simultane ous change in the setting of the regulator automatically upon operation of the same control means. This eliminates many of the parts formerly employed in systems of this character, in which a plurality of separate relays were provided for changing the adjustment of the regulator under manual control, and also avoids the necessity of making these adjustments separate from the operation of the tap-changing mechanism for the transformer supplying power to the furnace. The control circuits are further simplified in that it is possible to make use of a motor-operated mechanism which operates through a sequence of tap-changing steps always in the same direction, thus eliminating the formerly used reversing type motor and the more complicated control required to effect the desired tap change in the use of systems operated by such reversing motor.

The system in accordance with the present in- 55 vention is still further simplified from an operating standpoint in that the master control switch is operated to a single position only, de pending upon the desired change in both the tapchanging mechanism and the voltage adjusting mechanism, thus avoiding the necessity of a series of operations when the tap-changing mechanism is to be operated through several tapchanging steps.

It is an object of my invention to provide a furnace regulator system of the above-indicated character in which means is provided for automatically changing the setting of the regulator upon a change in the voltage of the supply circuit for supplying power to the furnace.

More specifically, it is an object of the invention to provide means for varying the adjusting resistors of the voltage coil of a furnace regulator of the movable electrode type simultaneously with the operation of the tap-changing mechanism associated with the transformer supplying power to the furnace.

Further objects and advantages of the invention will be apparent from the following descripetion of a preferred embodiment, reference being made to the accompanying drawing, in which the single figure illustrates the circuits and apparatus employed in said embodiment.

Referring to the drawing, an arc furnace structure is illustrated at I having a conducting casing shown grounded at 2 and adapted to contain a bath of metal or similar material 3 to be heated. The furnace is likewise provided with three movable electrodes 4, 5 and 6 connected by conductors l, 8 and 9, respectively, to the secondary winding l2 of a transformer bank having primary windings 13 shown connected in delta and supplied from circuit conductors I4, I5 and 16 from a three-phase, alternating-current source as controlled by a circuit breaker l1.

Furnace regulating equipment is provided for each of the three electrodes 4, 5 and 6, the equipment for operating electrode 4 only being illustrated for the sake of simplicity, and comprising a cable l8 for raising and lowering the electrode which passes over a pulley l9 above the electrode, and a reel 22 that is operated by a motor 23 having field windings 24 and 25 upon the flow of current from a source 26 as controlled by a regulator 21.

The regulator 2'! comprises a movable beam 28 mounted on a pivot 29 and normally held in its mid or balanced position by spring members 3| and 32. Two electromagnets are provided connected to the lever 28 at opposite ends thereof one comprising a current coil 33 connected by conductors 34 and 35 to a current transformer 36 to be energized in accordance with the current flowing in the conductor 1 to the electrode 4. The other electromagnet is provided with a voltage coil 31, one side of which is connected by conductor 38 to the furnace casing I, and the other side of which is connected through conductor 39 and selected resistor elements 4|, 42, 43 and 44 to conductor 1 in accordance with the voltage existing between the electrode 4 and the furnace casing.

A tap-changing mechanism is provided for changing the tap connections of the primary winding l3 of the transformer, shown as including a movable contact member 45 for the mechanism associated with each phase of the transformer and a plurality of fixed contact members 46, 41, 43 and 49 corresponding to four tap positions. The tap-changing mechanism is operated by a suitable mechanical means which is herein illustrated as a simple shaft 52 that is controlled by a motor 53 having an arma ture winding 54 and a field winding 55 that are supplied with direct-current energy from supply conductors 56 and 51. The shaft 52 also operates a cam 58 for controlling cam switches 6|, 62, 63 and 64 corresponding to the four tap positions of the tap-changing mechanism and which serve as limit switches for interrupting the operation of the tap-changing mechanism as it reaches a selected tap position. The apparatus is controlled by a master switch 65 having an operating handle 66 and a shaft 61 for actuating the three contact members 63, 69 and 10 to any one of four operating positions indicated by the four slots 1|, 12, 13 and 14 in a locking mechanism into which the arm 15 is adapted to be positioned. A spring member 16 is provided, one end of which engages a fixed abutment 11, which also serves as a guide for the shaft 61, and a. movable abutment 18 attached to the shaft 61 for. biasing it toward the left, as viewed in the drawing, to effect pressure between the. several contact members 68, 69 and 10 with their cooperating. contact members.

The circuit breaker I1 is provided with an opening magnet having a winding 8| through which a circuit may be completed from a battery 82 upon operation of a pushbutton switch 83 to a circuit closing position and a magnet having a closing winding 84. that may be energized from the battery 82 upon closure of the pushbutton switch 85. The magnets having windings BI and 84 operate the circuit breaker to its circuit-closing position in a well-known manner, and likewise operate interlock contact members 86 and 81 to their circuit-closing positions upon the opening of the circuit breaker l1 to connect the supply conductors. 56 and 51, respectively, with circuit conductors 8B and 89 for a purpose to be later explained.

If the tap-changing mechanism isin its illustrated or first position, the entire primary windings of the transformer are connected between the circuit conductors l4, l5- and 16, thus impressing a minimum voltage per turn on the primary windings and also on the secondary windings to supply a minimum voltage to the electrodes of the arc furnace. of the tapchanging mechanism, it will be noted that the contact member 68 of the master control switch 65 is in its first position in engagement with the fixed contact member 91 closing In this position a circuit from conductor 1 through conductor 92, contact members 68 and SI and conductor 93 to shunt the several voltage adjusting resistors 4|, 42, 43 and 44 from the voltage coil 31 of the regulator 21. When voltage is now applied to the furnace, a voltage will appear on the winding 31 forcing the associated magnet core upwardly to cause engagement between contact members 94 and 95 to close a circuit from the battery 26 through conductors 96 and 91, the field winding 24 and the armature winding of the motor 23 to effect operation of the motor in a direction to move the electrode downwardly. As the electrode is moved downwardly and engages the material 3 in the furnace, current will start flowing through the electrode 4 and the material to be melted, which material, upon the initial engagement of the electrodes therewith may have a relatively high resistance, thus permitting only a relatively small current flow. As the heating increases and the current through the electrode increases, the current in the current coil 33 of the regulator correspondingly increases and creates a force acting against the force of the voltage coil 31 until the current has increased to such a value that the magnetic pulls from the two coils 33 and 31 balance each other, and the contact member 94 again assumes its mid or illustrated position to interrupt the operation of the electrode motor 23. It will be noted that the three electrodes 4, 5 and 6 are connected in delta through the secondary winding l2 of the transformer supplying energy to the furnace, and that, as current flows through any one of the electrodes it must flow through at least one other of the three electrodes. The regulators for each of the three electrodes will so operate the electrodes that each electrode will ultimately carry the same current as the others.

As the current through the electrode increases above the value corresponding to a balance between the pulls exerted by the current coil 33 and the voltage coil 31, the contact member 94 will be moved downwardly into engagement with the contact member 98, closing a circuit from the battery 26 through conductor 99, motor field winding 25 and the motor armature to operate the motor 23 in a direction to raise the electrode 4 and decrease the current fiow therethrough until the pull on the windings 33' and 31 again balance, thus effecting separation of the contact members 94 and 93 to interrupt the operation of the motor 23.

When it is desired to change the value of voltage applied to the secondary circuit conductors 1, 8 and 9, the tap-changing mechanism is operated in the following manner. The circuit breaker pushbutton switch 85 is first pressed to energize the opening coil 84 and cause operation of the circuit breaker H to its current-interrupting position and at the same time closing the interlock switches 36 and 81, which is a necessary step before the tap-changing mechanism will operate. If it is desired to operate the mechanism from the first tap position, as illustrated, to the second tap position, the switch shaft 61 is moved in the abutments 11 and toward the right until the arm 15 is disengaged from the slot 1| and, at the same time, the contact member 69 is disengaged from the contact member IIJI for a purpose to be later explained. The switch shaft 61' is then rotated-toward the left until the arm 15 is in position opposite the slot 12 and slides into the slot 12 as the pressure on the handle 66 released and the spring I6 forces the shaft 61 again toward the left, causing engagement of the switch contact members 68, 69 and I0, respectively, with cooperating contact members I02, NH and I03. The switch contact member 68 closes a circuit from the conductor 1 through conductor 92, switch contact members 68 and I02 and conductor I04 in shunt to the resistors 42, 43 and 44, thus introducing the resistor 4| in circuit with the voltage coil 31 of the regulator. The purpose of this adjustment is to supply to the voltage coil 31 substantially the same voltage independently of the voltage supplied to the furnace electrode 4. The contact members 69 and I close a circuit from the supply conductor 56 through interlock switch 86, conductor 88, switch contact members Illl and 69, conductor I05, relay coil I06, conductor I01, limit switch 62, conductor I08, contact members I03 and I0, conductor 89, interlock switch 81 to supply conductor 51, thus causing the relay switch I09 to close and complete a circuit through the armature winding 54 of the motor 53 to operate the motor to move the cam 58 from its i1- lustrated position in a clockwise direction, thus moving the three tap-changing contact members 65 in each of the three phases from engagement with the fixed contact members 46 and into en gagement with the contact members 41. As the tap-changing mechanism reaches this position, the cam 58 will operate the limit switch 62 to interrupt the above-traced circuit through the relay winding !08, thus opening the relay switch I39 and interrupting the motor.

After the desired tap change has been effected, the circuit breaker closing pushbutton switch 83 may be pressed to energize the closing coil 8| for actuating the circuit breaker IT to its circuit closing position, after which the regulating mechanism will continue to operate in the manner previously described.

If it is desired to select any other tap position of the mechanism, the master switch 65 may be operated to either its third or fourth position corresponding to the arm I being positioned in the slot I3 or I4, respectively, by first manually operating the handle 6% to slide the shaft 67 toward the right, as illustrated, and rotating it to the proper selected position, thereby permitting the arm I5 to enter the associated slot. This movement of the switch moves the contact member 68 to engage either the contact member I I I to close a circuit through conductor I I2, or the contact member M3 to close a circuit through conductor I I4 to shunt from the circuit of the voltage coil 31 of the regulator the number of the adjusting resistors 4!, 42, 43 and 44 necessary to cause the application of substantially the same voltage to the coil 37 independently of the particular voltage applied to the furnace electrode. Similarly, the contact member I0 will be brought into engagement with the fixed contact member H5 or II6 to close a circuit either through conductor III and the limit switch 63 or conductor I I8 and the limit switch 64 to perform the same function described above with respect to the limit switch 62.

The operation of th control switch 65 to any one of its four selected positions establishes a control circuit for the winding I06 of the relay I09 effecting the operation of the motor 53 in the same directon, and continuing that operation until the limit switch GI, 62, 53 or 64 corresponding to the position of the master switch 65 interrupts the motor circuit and stops the motor on the selected position. The separation of the contact member 69 from the contact member l0l as the master switch 65 is moved from a selected number of its four positions to another position is for the purpose of preventing the relay winding I08 from becoming energized as the switch is moved from one selected position to another in cases where it is moved through more than a single step. In this manner, the operating circuit of the tap-changing motor 53 is not completed until the switch is in its final position corresponding to the selected operation desired.

It wil be appreciated that a regulator 21 and motor 23 and the control circuits therefor are provided for each one of the electrodes 4, 5 and E and that the master control switch 65 will be provided with a contact 68 and the contact members and circuits associated therewith for each one of the three regulators, one only of which is shown for the sake of simplicity.

It will be apparent to those skilled in the art that modifications may be made in the circuits and apparatus illustrated and described, and I do not wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention:

1. In a furnace-regulator system, the combination with a movable electrode and a motor for raising and lowering the electrode, of a regulator for governing the operation of the motor to maintain a constant arc and having two electromagnets connected to exert opposing pulls, one of said electromagnets having a current coil responsive to the current flowing in said arc and the other of said electromagnets having a voltage coil responsive to the voltage of the arc, a transformer for supplying electric energy to said furnace electrode and having tap-changing mechanism for varying the voltage of said supply, and means for operating the tap-changing mechanism and simultaneously adjusting the setting of the regulator.

2. In a furnace-regulator system, the combination with a movable electrode and a motor for raising and lowering the electrode, of a regulator for governing the operation of the motor to maintain a constant arc and having two electromagnets connected to exert opposing pulls, one of said electromagnets having a current coil responsive to the current flowing in said arc and the other of said electromagnets having a voltage coil responsive to the voltage of the arc, a plurality of regulator adjusting resistor elements for varying the setting of the regulator, a transformer for supplying electric energy to said furnace electrode provided with tap-changing mechanism, control means therefor including a switch for simultaneously selecting a predetermined operation of said motor and selection of said regulator adjusting resistors.

3. In a furnace-regulator system, the combination with a movable electrode and a motor for raising and lowering the electrode, of a regulator for governing the operation of the motor to maintain a constant arc and having two opposing elements, one actuated by a current coil responsive to the current flowing in said are and the other actuated by a voltage coil responsive to the voltage of the arc, a plurality of regulator adjusting resistor elements for varying the setting of the regulator, a transformer for supplying electric energy to said furnace electrode provided with tap-changing mechanism, control means for operating the tap-changing mechanism and for simultaneously varying the number of adjusting resistor elements in series with the voltage coil of said regulator to maintain a substantially similar voltage range on said regulator voltage coil for the same arc voltage for any tap position of the mechanism.

4. In a furnace-regulator system, the combination with a movable electrode and a motor for raising and lowering the electrode, of a regulator for governing the operation of the motor to maintain a constant arc and having two actuating elements connected to exert opposing pulls, one of said elements having a current coil responsive to the current flowing in said arc and the other of said elements having a voltage coil responsive to the voltage of the arc, means in circuit with said voltage coil for adjusting the setting of said regulator, voltage adjusting means for supplying electric energy to said furnace electrode at any one of a plurality of voltage steps, motor operated mechanism operable in one direction only I throughout a predetermined sequence of said steps for actuating said voltage adjusting means, a control means for controlling the operation of said mechanism to a selected one of said steps and for simultaneously adjusting the setting of said regulator.

5. In a furnace-regulator system, the combination with a movable electrode and a motor for raising and lowering the electrode, of a regulator for governing the operation of the motor to maintain a constant arc and having a current coil responsive to the current flowing in said are and a voltage coil responsive to the voltage of the are, a plurality of resistor elements associated with the voltage coil circuit for adjusting the setting of the regulator, voltage adjusting means for supplying electric energy to said furnace electrode at any one of a plurality of voltage steps, motor operated mechanism operable in one direction only throughout a predetermined sequence of said voltage steps for actuating said voltage adjusting means, control means including a limit switch associated with each step for stopping the motor operated mechanism on a selected step, and means for initiating the operation of the motor operated mechanism to a selected step and for simultaneously adjusting the resistor elements in series with the voltage coil of the regulator in accordance with the selected voltage step.

6. In a furnace-regulator system, the combination with a movable electrode and a motor for raising and lowering the electrode, of a regulator operative to maintain a balance between two opposing forces for governing the operation of the motor to maintain a desired arc, one of said 1 of said regulator as the voltage applied to the said are is varied, to reset the regulator for maintaining a balance between the pull exerted by the current coil and the pull exerted by the voltage coil for the new voltage supplied to the are over a similar voltage range on said regulator voltage coil.

7. In a furnace-regulator system, the combination with a movable electrode and a motor for raising and lowering the electrode, of a regulator operative to maintain a balance between two opposing forces for governing the operation of the motor to maintain a desired arc, one of said forces being determined by a current coil responsive to the current flowing in said arc and the other of said forces being determined by a voltage coil responsive to the voltage across the arc, circuit adjusting means in circuit with said voltage coil for adjusting the setting of said regulator, voltage adjusting means for supplying electric energy to said furnace electrode at any one of a plurality of voltage steps, motor operated mechanism operable in one direction only throughout a predetermined sequence of said steps for actuating said voltage adjusting means, a control means for controlling the operation of said motor operated mechanism to a selected one of said steps and for simultaneously adjusting the setting of said circuit adjusting means for adjusting the arc voltage at which the pull exerted by the current coil will balance the pull exerted by the voltage coil proportionally to changes in the voltage applied across the arc.

8. In a furnace-regulator system, the combination with a movable electrode and a motor for raising and lowering the electrode, of a regulator operative to maintain a balance between two opposing forces for governing the operation of the motor to maintain a desired arc, and having one of said forces being determined by a current coil responsive to the current flowing in said arc and the other of said forces being determined by a voltage coil responsive to the voltage across the arc, a plurality of resistor elements associated with the voltage coil circuit for adjusting the setting of the regulator, voltage adjusting means for supplying electric energy to said furnace electrode at any one of a plurality of voltage steps, motor operated mechanism operable in one direction only throughout a predetermined sequence of said voltage steps for actuatin said voltage adjusting means, control means including a limit switch associated with each step for stopping the motor operated mechanism on a selected step, and means for initiating the operation of the motor operated mechanism to a selected voltage step position and for simultaneously adjusting the resistor elements in series with the voltage coil of the regulator in accordance with the selected voltage step for maintaining a substantially constant balanced pull exerted by said current coil and said voltage coil over substantially similar current and voltage ranges for any voltage step position of the motor operated mechanism.

JAMES P. HOUCK. 

